We do offer it on a root w/ encryption.  But as you just said, they can still snapshot memory as ALL email has this issue.
But there is still privacy above what proton has, and you get other services such as XMPP and Cryptpad with it, so its good for small businesses that need email to function 

 I meant root server as in contrary to vps. of you have exclusive hardware, you have a shot at real privacy. 

 Oh.  That'd be hella expensive for just email only.  But if you have a bunch of other stuff running too, then yeah